1. Field of the Invention
The present invention relates to autoclaved inorganic building materials with solid particulate hydrophobic silicone resin(s) uniformly incorporated therein, and to processes of making the same.
2. Background Art
Conventional inorganic matrix building materials, including artificial stones, concrete blocks, and fiber-reinforced concrete boards, can be subject to efflorescence and freeze thaw damage which are commonly known to be associated with water absorption into and through the building materials. For example, moisture penetration into even natural permeable stone substrates can cause these materials to expand, to crack, and to cause ultimate deterioration of the structure of the building materials. Water moisture also greatly induces microbial invasion and attack, often resulting in unsightly discoloration. Masonry materials based on inorganic binders may suffer the same type of degradation due to freeze/thaw conditions, resulting in what is known as spalling and cracking.
A material's susceptibility to water absorption is thus often manifested in lower resistance to water damage, higher water permeability, higher water migration, and/or lower freeze thaw resistance. It has been the emphasis of the technical field to prevent or reduce water absorption into the building materials.
It is known in the art to apply hydrophobing agents to a surface of the building material to confer hydrophobicity, wherein the hydrophobing agents are often delivered as a solution, emulsion, or dispersion, and applied to the surface as a coating or a sealer. The solvent or liquid phase may be water or an organic liquid or mixture thereof. From an environmental standpoint, water is preferred as the solvent or continuous phase to avoid VOC emissions.
In masonry work, for example of stone, concrete block, brick, etc., water travels not only horizontally from the face of the structure, but also vertically from adjoining mortar and stone, brick, etc. Thus, hydrophobicizing the surface following construction only limits ingress of water from the outside surface. Water traveling vertically may still enter the masonry product and cause efflorescence and freeze/thaw damage. However, if all sides of the construction material are hydrophobicized prior to construction, the hydrophobic coating may prevent adherence of mortar, or subsequent application of plasters, renders, stucco, etc.
U.S. Pat. No. 4,076,868 to Roth et al. discloses a process for cleaning and rendering building materials hydrophobic. The process includes applying to the surface of the building material a solution of a hydrophobing agent having admixed therewith a filler and after evaporation of the solvent, removing the filler residue.
U.S. Pat. No. 5,063,087 to Eck et al. discloses a process for improving the adhesion of polymeric substances containing organic groups to surfaces having alkaline earth metal carbonates in which a solution of phosphorus-containing organosilicon compound is applied to a surface containing an alkaline metal carbonate, the solvent is removed and then a polymeric substance containing organic groups is applied to the treated surface.
U.S. Pat. No. 4,600,657 to Wegehaupt et al. discloses a method for coating asphaltic concrete. The method includes applying a crosslinkable composition containing a diorganopolysiloxane and rod-shaped styrene-n-butyl acrylate copolymers which are obtained from the free-radical copolymerization of monomers in the presence of the diorganopolysiloxane, and thereafter crosslinking the diorganopolysiloxane composition to form an elastomeric coating on the asphaltic concrete.
The above-described hydrophobing surface coating compositions or processes for rendering a surface hydrophobic, however, have met with limited use. For these compositions and processes, a primer is often needed as a base coating before the hydrophobing surface coating or sealer may be applied. Moreover, even before the primer or the base coating is deposited onto the surface, the surface has to be subjected to laborious pretreatment with water or acid vapor, or by sandblasting. This is particularly so when the building materials have been exposed to the atmosphere for quite some time and thus have been rendered dirty by dust or waste gases. All the above-described methods of hydrophobicizing building materials also suffer from complex methods of preparation and application, and are also generally subject to discoloration after extended exposure. The degree of hydrophobicity may also decrease over time. The pre-treatment steps along with the base coating applications thus inevitably cause the use of these hydrophobing surface coatings to be more time consuming, more labor intensive, and much less cost effective.
More recently, emulsions of organopolysiloxanes, silanes, and combinations thereof have been used to hydrophobicize external surfaces of building materials. Examples of these include U.S. Pat. No. 5,661,196 (Mayer et al.) which discloses self-dispersing organopolysiloxanes which may be coated onto building materials from aqueous emulsion; U.S. Pat. No. 5,962,585 (Mayer et al.) which discloses a stiff cream of an alkylalkoxysilane or alkoxy group-containing organopolysiloxane with a basic nitrogen-containing organopolysiloxane, the stiff cream being an aqueous cream stabilized through use of an emulsifier; U.S. Pat. No. 5,985,994 (Oberneder et al.) which discloses an aqueous dispersion of an organopolysiloxane containing condensable groups, a branched alkoxysilane, and an organosilicon compound containing basic nitrogen; U.S. Pat. No. 6,294,608 (Hager, et al.) which discloses emulsifier-stabilized aqueous emulsions of alkoxysilanes or branched organopolysiloxane containing alkoxy groups with silanes or branched organosiloxanes containing aminoalkyl groups; and U.S. Pat. No. 6,492,459 (Hager et al.), an emulsifier-stabilized aqueous cream containing alkoxysilanes or alkoxy-functional organopolysiloxanes and organic solvent. Organopolysiloxane resins are disclosed, for example, as an optional component in U.S. Pat. No. 6,492,459, the resin being dissolved in low viscosity silanes, organopolysiloxanes, or organic solvent.
The organosilicone based compositions described above have proven useful in hydrophobicizing existing masonry work such as building facades, retaining walls, tunnels, etc., but are only capable of hydrophobicizing the surface. Applications involving stiff creams are labor intensive, and the presence of organic solvents in some of the compositions described is not desirable in view of present day limitations on VOCs. These compositions reduce, but do not eliminate, freeze-thaw damage, and may be subject to discoloration after long term exposure.